Effects of Chemical Antitranspirants on Transpiration and Growth of Grass

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Abstract
The effects of foliar sprays of the metabolic inhibitors dodecenylsuccinic acid (DSA) and phenylmercuric acetate (PMA), as antitranspirants, were tested on grass grown outdoors (in lysimeters), but more accurate tests were made with PMA in growth rooms, using small weighable transpirometers. Concentrations of PMA which were weaker than 10-3.8 M resulted in only slight reductions in transpiration, whereas concentrations stronger than 10-3.2 M were phytotoxic, though water losses were reduced by about 30 per cent. PMA at 10-3.5 M gave the greatest decrease in transpiration (about 20 per cent) without reducing growth, but its effectiveness depended on the amount applied per unit area of vegetation. The effects of PMA also differed with plant species and with environment, being greatest under conditions of low soil moisture stress and temperature. The antitranspirant reduced stomatal apertures and increased leaf temperatures.